Narcissists may seem to love themselves, but a new study finds that narcissistic self-aggrandizement may hide deep feelings of inferiority.

According to the new research, people who are narcissistic are likely to tell psychologists that they feel good about themselves. But when the psychologists trick these narcissists into thinking they’re hooked up to a working lie-detector test, the truth comes out and the narcissists admit to lower self-esteem.

“This suggests that individuals with high levels of narcissism may be inflating their self-esteem,” study researcher Erin Myers, a psychologist at Western Carolina University, told LiveScience. “In other words, narcissistic individuals may not really believe they are as great as they claim to be.”